feat: test and document access-token prefix support

src/libfetchers/fetch-settings.hh

@@ -23,9 +23,11 @@ struct Settings : public Config
           Access tokens are specified as a string made up of
           space-separated `host=token` values.  The specific token
           used is selected by matching the `host` portion against the
-          "host" specification of the input. The actual use of the
-          `token` value is determined by the type of resource being
-          accessed:
+          "host" specification of the input. The `host` portion may
+          contain a path element which will match against the prefix
+          URL for the input. (eg: `github.com/org=token`). The actual use
+          of the `token` value is determined by the type of resource
+          being accessed:
 
           * Github: the token value is the OAUTH-TOKEN string obtained
             as the Personal Access Token from the Github server (see

src/libfetchers/fetchers.hh

@@ -264,6 +264,9 @@ struct InputScheme
 
     virtual std::optional<std::string> isRelative(const Input & input) const
     { return std::nullopt; }
+
+    virtual std::optional<std::string> getAccessToken(const fetchers::Settings & settings, const std::string & host, const std::string & url) const
+    { return {};}
 };
 
 void registerInputScheme(std::shared_ptr<InputScheme> && fetcher);

src/libfetchers/github.cc

@@ -172,7 +172,7 @@ struct GitArchiveInputScheme : InputScheme
         return input;
     }
 
-    std::optional<std::string> getAccessToken(const fetchers::Settings & settings, const std::string & host, const std::string & url) const
+    std::optional<std::string> getAccessToken(const fetchers::Settings & settings, const std::string & host, const std::string & url) const override
     {
         auto tokens = settings.accessTokens.get();
         std::string answer;